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Friday, December 8, 2017

On December 08, 2017 B. Skiff reported on mpml mailing list, that the centaur 174P/Echeclus (also known as 60558 Echeclus) "seems to be at least 4 mag brighter than expected, and indeed as it appeared at the start of last night's images. The Dec 7 series shows the outburst in progress on images taken near 2:00 and 2:48 UT; it is much brighter now (Dec 8 about 3:30 UT)". Last observations before this outburst had this object at around magnitude 18.

Prompted by this alert, I perfomed some follow-up of 174P/Echeclus and I can confirm that this object is experiencing a bright phase. Unfiltered exposures, 30-seconds each, obtained remotely from Q62 (iTelescope network) on 2017, December 08.57 (through a 0.50-m f/6.8 astrograph + CCD + f/4.5 focal reducer) reveal 174P as a bright featureless star-like object of magnitude ~14.1 N (click on the image below for a bigger version).

This very interesting object was discovered by Spacewatch in 2000 and initially classified as a minor planet with provisional designation 2000 EC98 (its final minor planet designation is 60558 Echeclus). The presence of coma around it was first detected by Choi and Weissman (2006) on 2005 December 30.50 UT with the Palomar 5m telescope. Soon after, the object was given the periodic comet designation 174P/Echeclus. During the years, it experienced many outbursts. You can find info and images on all these past bright phases on this blog.

Sunday, November 12, 2017

During the month of July 2017, 2 new comets were discovered and cometary activity was detected for 1 previously discovered object (earlier designated as an asteroid). "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram) which reported the official news & designations.

* Note on CBET 4426 issued on August 26: After considerable discussion, the IAU "Working Group for Small Body Nomenclature" (formerly the IAU "Committee for Small Body Nomenclature" and the IAU "Small Bodies Names Committee") has decided to accept the name "ASASSN" for comet C/2017 O1 (cf. CBET 4414).

Jul 12 CBET 4413 report the discovery of an apparent satellite (S/2017 (113) 1) of minor planet (113) Amalthea from observations made of the Tycho Catalogue star 1878-01081-1 (magnitude V = 10.0) during an occultation by the minor planet (which was at V = 12.9) on 2017 Mar. 14.167 UT. A total of ten observation sites recorded seven positive events and three negative events for (113), two of which are attributed to the possible satellite.

After exactly 5 years, 2012 TC4 will have a new close approach with our planet that will provide astronomers with a valuable opportunity to learn more about its orbit and composition and to test the network of observatories and scientists who work with planetary defense. This asteroid was not observed since the week it was discovered in October 2012 and it has been recovered by astronomers using one of the European Southern Observatory's 8.2-meter telescopes at the Very Large Telescope (VLT) on July 27, 2017 at an apparent magnitude of 26.8 (making it the faintest Near Earth Asteroid so far measured).

Credit: ESO/ESA NEOCC/Hainaut (ESO), Micheli (ESA) & Koschny (ESA)

2012 TC4 has an estimated size of 12 m - 27 m (H=26.7) and it will have a close approach with Earth at about 0.13 LD (Lunar Distances = ~384,000 kilometers) or 0.00034 AU (1 AU = ~150 million kilometers) at 0542 UT on 12 Oct. 2017 and it will reach the peak magnitude ~13. (For comparison, the asteroid that hit Earth’s atmosphere near Chelyabinsk, Russia, in February 2013 was roughly 20 meters across). The rapid rotation and lightcurve amplitude (rotation period of 0.2038 hours with a brightness variation of 0.93 magnitude) suggest that the 2012 TC4 is an elongated, monolithic body (a rubble pile would have spun itself apart). Non-principal axis rotation suggests that it probably has a complex (non-ellipsoidal) shape. 2012 TC4 should be detectable at Goldstone from about Oct. 9 - 16, but not at the moment of closest approach, when it will be too far south for Goldstone to track.

Below you can see my image (single 120-second exposure) of 2012 TC4 obtained on 2017, Oct. 11.35, few hours before its close approach. At the moment of the shot, the asteroid was of magnitude ~15.9 and moving at ~24"/min. The asteroid is trailed in the image due to its fast speed. Click on the image below to see a bigger version. (North is up, East is to the left).

The short animation below is showing the movement of 2012 TC4 (two consecutive 120-second exposure). Click on the thumbnail below to see the animation (North is up, East is to the left).

Thanks to the new observations following its 2017 recovery, it became clear that new orbit solution precludes a possible impact in 2050: "2012 TC4 would miss the keyhole that would lead to an impact with Earth in 2050. This plot shows the b-plane—the asymptotic location of TC4 relative to the Earth before the Earth's gravity starts bending the trajectory of TC4. The b-plane intersections for progressive orbit solutions is shown by the ellipses (dashed lines show 1-σ uncertainties, solid lines show 3-σ uncertainties), while the red dots show the b-plane coordinates that lead to an impact in 2050. Starting with the Sept 28 solution, the 3-σ uncertainites fall well clear of the red dots, indicating that the asteroid will miss the Earth in 2050. Future impacts beyond that date have not been ruled out."

Tuesday, September 12, 2017

During the month of June 2017, 6 new comets were discovered and there were 4 comet recoveries. "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram) which reported the official news & designations.

Jun 5 CBET 4401 reports that minor planet (9972) MINORUODA is a binary system with an orbital period of 22.89 +/- 0.01 hr. The primary shows a period of 3.4221 +/- 0.0002 hr and has a lightcurve amplitude of 0.11 mag at solar phases 10-14 degrees, suggesting a nearly spheroidal shape. Mutual eclipse/occultation events that are 0.06- to 0.13-magnitude deep indicate a lower limit on the secondary-to-primary mean-diameter ratio of 0.24.

Jun 13 CBET 4403 provide the following update by Jenniskens & Lyytinen on expected meteor activity from long-period comet C/2015 D4, now that an improved comet orbit is available (cf. CBET 4127). Based on an orbit for C/2015 D4 calculated by G. V. Williams from 43 observations spanning 2015 Feb. 23-Oct. 15 (cf. MPEC 2015-U54), the position of the one-revolution dust trail was calculated for the period 1996-2070. Results show that the dust trail will be in the earth's path on 2017 July 29d00h22m UT (solar longitude 125.858 deg), when the earth passes the center of the trail at a relative distance of only r - Delta = +0.0006 AU; the earth will thus pass inside the comet's orbit at a time when the comet has just passed perihelion, both favorable circumstances for detecting meteors. Meteors are expected from geocentric R.A. = 79 deg, Decl. = -32 deg, with geocentric velocity 45.9 km/s.

Jun 20 Images of asteroid 6 Hebe taken using SPHERE instrument on ESO ’s Very Large Telescope and related research paper http://bit.ly/2tnC9hR

Jun 22 New paper on Arxiv by D. Nesvorny et al.: "Origin and Evolution of Short-Period Comets". In the panel below, extracted from the paper, the orbital distribution of known SPCs. The thin lines show the division between between ECs and NICs (panel b; TJ = 2).

Credit: Nesvorny et al.

Jun 24 CBET 4409 reports that comet C/2015 ER61 (PANSTARRS) has evidently experienced a splitting: a companion fragment (denoted 'B') was reported by E. Bryssinck (Kruibeke, Belgium) from CCD images taken by F.-J.Hambsch (Mol, Belgium) and himself on June 13, 15, and 16 remotely with a 0.4-m f/6.8 reflector (both unfiltered and with a Bessel R filter) at the private "ROAD Observatory" located at San Pedro de Atacama, Chile; Bryssinck noticed a change over a couple of days in the shape of the nuclear condensation, followed by the appearance of a possible nuclear fragment inside the coma and tail. On June 13.41 UT, seven exposures show a very faint fragment located 12".3 from the main nuclear condensation in p.a. 243 degrees with a diameter of 8" (magnitude R = 16.5 in an aperture of diameter 5".4). Seven images taken on June 15.42 show the very faint fragment 13".0 from the main condensation in the same direction and with magnitude R = 16.6 in the same-sized aperture. Nine images taken on June 16.41 show component B at size 8".8 (with R = 16.6 in a 5".4 aperture) and located 13".4 from component A in p.a. 248 deg. Component B is difficult to see due its small distance from component A and to its location within the tail.

Friday, August 4, 2017

During the month of May 2017, 2 new comets were discovered and cometary activity was detected for 1 previously discovered object (earlier designated as an asteroid). "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here). See below for the "Other news" section.

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram) which reported the official news & designations.

May 02 H. H. Hsieh reports on CBET 4388 that r'-band observations taken on Apr. 26 and 29 with the Gemini South Observatory (seven 100-s exposures per night; queue observer J. Chavez) show that comet 259P (cf. IAUC 8969; CBET 3115), which has been previously identified as an active minor planet and main-asteroid-belt comet candidate, is currently active. According to CBET 4388: "Including its previously observed active apparition in 2008 (IAUC 8969), these observations mark the second time that comet 259P has been seen to be active. The fact that 259P exhibits regularly repeated periods of activity, interspersed with periods of quiescence, is a strong indicator that its activity is driven by the sublimation of volatile material, consistent with its initial identification as an ice-bearing main-asteroid-belt comet."

May 18 Hubble Spots Moon Around "2007 OR10", Third Largest Dwarf Planet in the Kuiper Belt. The team's results appeared in The Astrophysical Journal Letters: "2007 OR10 is currently the third largest known dwarf planet in the trans-Neptunian region, with an effective radiometric diameter of ∼1535 km. It has a slow rotation period of ∼45 hr that was suspected to be caused by tidal interactions with a satellite undetected at that time. Here, we report on the discovery of a likely moon of 2007 OR10, identified on archival Hubble Space Telescope WFC3/UVIS system images."

May 24 CBET 4394 reports that minor planet (190166) 2005 UP156 is a fully-synchronous binary system with an orbital/rotational period of 40.542 +/- 0.008 hr. The V magnitude was 16.0 on May 4, brightening to 15.2 on May 23. The out-of-eclipse lightcurve shows an amplitude of about 0.5 magnitude with eclipse attenuations of about 0.6 mag. The deeper event lasts about 2.8 hours. The effective secondary-to-primary diameter ratio is estimated to be 0.8 +/- 0.1.

May 26 A possible impact flash on #Jupiter was imaged by on May 26 by S. Pedranghelu with at least 2 independent confirmations. More info on see our blog post here

Tuesday, July 25, 2017

CBET nr. 4414, issued on 2017, July 24, announces the discovery of a comet (magnitude ~15.3) in the course of the "All-Sky Automated Survey for Supernovae" (ASASSN) program, from images taken with the 14-cm "Cassius" survey telescope at Cerro Tololo on July 19.32 UT. The new comet has been designated C/2017 O1.

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 60 seconds each, obtained remotely on 2017, July 23.7 from Q62 (iTelescope network) through 0.50-m f/6.8 astrograph + CCD + f/4.5 focal reducer, shows that this object is a comet with a sharp central condensation surrounded by diffuse coma about 3 arcmins in diameter

Below you can see a graph generated using the software Orbitas and showing the predicted magnitude for this comet (click on the image for a bigger version). Visual estimates have the comet at mag. ~10 on July 24, 2017. Syuichi Nakano, Sumoto, Japan, notes on CBET 4414 that this comet could reach total visual magnitude 7 during September-November.A word of caution: as always with comets, the future magnitudes reported here are only indicative.

UPDATE - August 26, 2017

According to CBET 4426: "After considerable discussion, the IAU "Working Group for Small Body Nomenclature" (formerly the IAU "Committee for Small Body Nomenclature" and the IAU "Small Bodies Names Committee") has decided to accept the name "ASASSN" for comet C/2017 O1 (cf. CBET 4414)."

Apr 20 Radar images of 2014 JO25 from @NAICobservatory reveal shadows, possible boulders, and more on this 650+ m (twice as big as previously estimated) asteroid rotating in ~4.5 hours: "Arecibo radar observations revealed the asteroid to have a lumpy, two-lobed shape very reminiscent of Comet 67P/Churyumov–Gerasimenko recently visited by the European Space Agency's Rosetta mission."

Credit: Arecibo Obs./NASA/NSF

Apr 29 CBET 4387 reports that minor planet (2881) is a binary system with an orbital period of 20.42 +/- 0.01 hr. Mutual eclipse/occultation events that are 0.09- to 0.15-magnitude deep indicate a secondary-to-primary mean-diameter ratio of 0.29 +/- 0.02.

Sunday, June 4, 2017

CBET nr. 4397, issued on 2017, June 01, announces the discovery of a comet (magnitude ~17) by the "Asteroid Terrestrial-impact Last Alert System" (ATLAS) Team on CCD exposures taken on May 26.5 with the ATLAS 0.5-m f/2.0 Schmidt telescope at Haleakala. The new comet has been designated C/2017 K4 (ATLAS).

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 120 seconds each, obtained remotely on 2017, May 29.4 from Q62 (iTelescope network) through 0.43-m f/6.8 reflector + CCD, shows that this object is a comet with a diffuse coma nearly 10 arcsec in diameter

Wednesday, May 31, 2017

On May 26, 2017 (between 19:24.6 and 19:26.2 Universal Time) a new possible impact flash on Jupiter was imaged by Sauveur Pedranghelu, a French amateur astronomer from Corsica. According to a preliminar analysis by Marc Delcroix (who runs a Jovian impact flashes detection project) this flash, detected in the North polar area of Jupiter, seems shorter than the others (~0.7s vs 1-2s) and displayed two brightness peaks. (click on the images below for a bigger version).

The image by Pedranghelu was then posted online as a call for observations of Jupiter obtained in the same time interval to exclude the possibility that the flare might have been caused by an artefact or flashing satellite. Few hours after the posting, two other observers from Germany (Andre Fleckstein& Thomas Riessler) confirmed independently from one another the finding with their own images.

Below you can see an animation made by Thomas Riessler using his Jupiter observations showing the impact flash on Jupiter. (click on it for a bigger version). The impact area imaged in the hours after the reported flash showed NO remnants of the impact.

In this blog we reported about all the recent cases starting from the event of July 19, 2009 (a scar left on Jupiter by an unseen impact observed by Anthony Wesley), of June 03, 2010 (impact flash observed by Anthony Wesley and Christopher Go), of August 20, 2010 (impact flash observed by Masayuki Tachikawa & Aoki Kazuo), of September 10, 2012 (impact flash observed by Dan Petersen and George Hall), of March 17, 2016 (impact flash observed by Gerrit Kernbauer and John McKeon).

The role of planet Jupiter as a shield protecting Earth from getting hit by such objects is still controversial and it has been discussed in depth in a series of articles by Jonathan Horner and Barrie Jones (Jupiter - friend or foe?).

Feb 09 New impact crater spotted on Mars: "This new crater, which formed explosively at the point of impact, has a diameter of roughly 8 meters (about 25 feet), but its surrounding blast zone and ejecta extend over a kilometer (about one mile) beyond the crater itself. This new impact was discovered using the lower-resolution Context Camera (CTX), also on board Mars Reconnaissance Orbiter. An older CTX image of this region from May 2012 shows a uniformly dust-covered surface, while a newer CTX image from September 2016 reveals the crater’s dark blast zone.". Click on the image below for a bigger version.

Feb 13 Radar images of asteroid 2017 BQ6were obtained on Feb. 6 and 7 with NASA’s 70-meter antenna at GSSR. "They reveal an irregular, angular-appearing asteroid about 660 feet (200 meters) in size that rotates about once every three hours. The images have resolutions as fine as 12 feet (3.75 meters) per pixel.Asteroid 2017 BQ6 safely passed Earth on Feb. 6 at 10:36 p.m. PST (1:36 a.m. EST, Feb. 7) at about 6.6 times the distance between Earth and the moon (about 1.6 million miles, or 2.5 million kilometers). It was discovered on Jan. 26 by the NASA-funded Lincoln Near Earth Asteroid Research (LINEAR) Project, operated by MIT Lincoln Laboratory on the Air Force Space Command’s Space Surveillance Telescope at White Sands Missile Range, New Mexico." Click on the image below for a bigger version.

Credits: Credits: NASA/JPL-Caltech/GSSR

Feb 15 Arecibo Radar Observatory captures revealing images of Comet 45P/Honda-Mrkos-Pajdusakova : "The comet’s shape is probably two lobes and is seen here to be about 1.3 km in size. Gif below composed of thirteen delay-Doppler images of Comet 45P/HMP after 2 hours of observation. The new radar observations have revealed Comet 45P/HMP to be somewhat larger than previously estimated. The radar images suggest a size of about 1.3 km (0.8 mi) and that it rotates about once every 7.6 hours."

Credits: Arecibo Observatory/NASA/NSF

Feb 15 On this day, 4 years ago the Chelyabinsk meteor(15 FEBRUARY 2013). Click on the image below for a bigger version.

Saturday, March 18, 2017

During the month of January 2017, 4 new comets were discovered, cometary activity was detected for 1 previously discovered object (earlier designated as an asteroid) and there was 1 comet recovery. "Current comet magnitudes" & "Daily updated asteroid flybys" pages are available at the top of this blog (or just click on the underline text here).

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram) which reported the official news & designations.

Monday, March 13, 2017

CBET nr. 4373, issued on 2017, March 13, announces the discovery of a comet (magnitude ~15) by Terry James Lovejoy on three CCD 8-s exposures taken five minutes apart starting on Mar. 9.684 UT with a Celestron C14 reflector operating at f/1.9 (+ QHY9 camera). The new comet has been designated C/2017 E4 (LOVEJOY).

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 10 unfiltered exposures, 30 seconds each, obtained remotely on 2017, March 10.7 from Q62 (iTelescope network) through a 0.50-m f/6.8 astrograph + CCD + focal reducer, shows that this object is a comet with a diffuse coma nearly 15 arcsec in diameter.

Sunday, March 5, 2017

CBET nr. 4369, issued on 2017, March 04, announces the discovery of a comet (magnitude ~17) by Gennadii Vladimirovich Borisov on three unfiltered 120-s exposures obtained on Mar. 1.10 UT with a 0.4-m f/2.3 astrograph at the "Mobil Astronomical Robotics Genon" Observatory (MARGO) near Nauchnij. The new comet has been designated C/2017 E1 (Borisov).

I performed follow-up measurements of this object, while it was still on the neocp. Stacking of 20 unfiltered exposures, 30 seconds each, obtained remotely on 2017, March 1.5 from H06 (iTelescope network) through a 0.43-m f/6.8 reflector + CCD + f/4.5 focal reducer, shows that this object is a comet with a diffuse coma nearly 30 arcsec in diameter.

The dates below refer to the date of issuance of CBET (Central Bureau Electronic Telegram) which reported the official news & designations.

- Comet Discoveries

Dec 21 Discovery of C/2016 X1 (LEMMON)

- Other news

Dec 13 Image of the Kuiper belt object Orcus and its moon Vanth posted on twitter by M. Brown: "The ALMA radio telescope/interferometer detects the heat coming from Orcus ~4 billion miles away and separately from its moon Vanth."

Dec 20 Man-To Hui & David Jewitt published on Arxiv the follwing paper "Non-Gravitational Acceleration of the Active Asteroids" where they present an astrometric investigation of 18 active asteroids in search of non-gravitational acceleration. "Comets can exhibit non-gravitational accelerations caused by recoil forces due to anisotropic mass loss. So might active asteroids."

Dec 23 CBET 4339 reports that a group of observers obtained lightcurves of the minor planet (12008) KANDRUP during July 2007, which were typical of binary synchronous asteroids. "The period is around 1.371 day. "The monitoring until January 2008 showed a regular evolution of the signature of mutual phenomenona. Other observations were obtained between August and October 2010, showing lightcurves with similar properties. In December 2013, the amplitude of variation was similar to those of the other oppositions, but some events were possibly missed. As observed on 2016 Dec. 2 and 7, the mutual phenomenona are 0.5-magnitude deep and their duration is around 4 hours; an observed brightness minimum occurred on Dec. 6.930 UT. These are indications that the mutual orbit of the system components is close to the ecliptic plane, like that of minor planet (4492) Debussy".

Comets & Asteroids news

Welcome to our Astronomy blog, devoted in particular to Comets & Asteroids and related topics. This blog is maintained by Italian amateur astronomer Ernesto Guido, particularly active in the study of the small bodies of the Solar System.